A hybrid vehicle typically includes a high voltage battery (e.g. a battery which supplies energy or potential energy of about three hundred volts). The high voltage battery is typically used to operate a motor/generator assembly which selectively provides torque to the wheels of the vehicle. Such hybrid vehicles are typically divided into series hybrid electric vehicles (HEVs), parallel HEVs, and series-parallel HEVs. Hybrids that use a series drivetrain may receive mechanical power from the electric motor, which may be run by the high voltage battery, for example. For hybrids with parallel drivetrains, the electric motor and internal combustion engine can provide mechanical power simultaneously. Alternatively, hybrids with series/parallel drivetrains may enable the engine and electric motor to provide power independently or in conjunction with one another.
For hybrid vehicles designed to be performance vehicles, or vehicles designed and built specifically for speed capabilities, maximum performance at a test track or drag strip may dictate the need for rapid charging of the high voltage battery, particularly in a case where fast charging stations are not available. For a performance vehicle with an electric machine positioned in a driveline downstream of a dual clutch transmission (DCT), and with an integrated starter/generator (ISG) positioned upstream of the DCT, the electric machine cannot be used for charging when the vehicle is stationary, and thus only the ISG may be used for charging while the vehicle is stationary. Due to the positioning of the ISG and electric machine in such a vehicle, torque accuracy of the engine, ISG, and electric machine is extremely important during any aggressive charging of the battery.
The inventors herein have recognized these issues, and have developed systems and methods to at least partially address them. In one example, a method is provided, comprising charging a battery in a hybrid vehicle at a first rate via transferring torque from an engine to at least one motor/generator upstream of a transmission coupled to the engine and at least another motor/generator downstream of the transmission while vehicle speed is controlled based on a driver-demand, and charging the battery at a second rate via the upstream and downstream motor/generators while vehicle speed is autonomously controlled. In this way, a battery in a performance vehicle may be aggressively charged without negatively impacting drivability.
As one example of the method, the at least one motor/generator upstream of the transmission and the at least another motor/generator downstream of the transmission further comprises an integrated starter/generator positioned upstream of the transmission, and an electric machine positioned downstream of the transmission. In one example, the speed of the vehicle being controlled autonomously further comprises controlling vehicle speed to a target vehicle speed via a cruise control system. In some examples, the transmission may comprise a dual clutch transmission.
As an example, the method may include mechanically coupling the engine to the transmission while charging the battery at both the first rate and the second rate. Charging the battery at the first rate may further comprise a condition wherein a maximum charging power of the at least one motor/generator positioned upstream of the transmission is not greater than a driver-demanded wheel power by a predetermined threshold. For example, charging the battery at the first rate may include a total charging power of the at least one motor/generator upstream of the transmission and the at least another motor/generator downstream of the transmission to be a function of a predetermined amount of charging torque, or a predetermined percentage of a driver-demanded wheel torque, under conditions where the vehicle speed is controlled based on driver-demand, and where the maximum charging power of the at least one motor positioned upstream of the transmission is not greater than the driver-demanded wheel power by the predetermined threshold. As an example, the predetermined amount of charging torque may be 100 Nm, and the predetermined percentage of the driver-demanded wheel torque may be fifty percent of the driver-demanded wheel torque. Furthermore, the total charging power may equal a product of vehicle speed and the larger of the predetermined amount of charging torque, or the predetermined percentage of the driver-demanded wheel torque.
In yet another example, the method may further comprise mechanically decoupling the engine from the transmission, and charging the battery at a third rate via the at least one motor upstream of the transmission responsive to an indication that the maximum charging power of the at least one motor upstream of the transmission is greater than the driver-demanded wheel power by the predetermined threshold. In such an example, charging the batter at the third rate may comprise charging the battery at the maximum charging power of the at least one motor positioned upstream of the transmission.
In a still further example, charging the battery at the second rate may further comprise commanding each of the at least one motor/generator upstream of the transmission and at least another motor/generator downstream of the transmission to their respective maximum charging power. Furthermore, charging the battery at the second rate may further comprise adjusting engine torque while vehicle speed is autonomously controlled.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.